<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Input with Background Number</title>
    <style>
        .input-container {
            position: relative;
            display: inline-block;
        }

        .input-container::before {
            content: "0"; /* 伪元素内容 */
            position: absolute;
            left: 10px;
            top: 50%;
            transform: translateY(-50%);
            font-size: 24px; /* 调整字体大小 */
            color: rgba(0, 0, 0, 0.2); /* 调整颜色和透明度 */
            pointer-events: none; /* 防止伪元素干扰点击 */
        }

        .input-container input {
            padding-left: 30px; /* 为伪元素留出空间 */
            border: 1px solid #ccc;
            border-radius: 4px;
            background-color: transparent; /* 使背景透明 */
        }
    </style>
</head>
<body>
    <div class="input-container">
        <input type="text" placeholder="Enter a number...">
    </div>
</body>
</html>